In humans, alcoholism and depression are often interrelated. This study examines the effects of alcohol on peer separation-induced despair in rhesus monkeys, a proposed nonhuman primate model of depression. Alcohol, at three different dose levels, or placebo was administered to rhesus monkeys undergoing repeated peer separation. Low-dose alcohol (1 g/kg/day) decreased separation-induced despair, whereas high-dose alcohol (3 g/kg/day) exacerbated the despair response as compared to placebo. This biphasic effect of alcohol on the despair response may be analogous to similar effects of alcohol on depression in humans.